scholarly journals In VitroAntibiotic Susceptibilities of Yersinia pestis Determined by Broth Microdilution following CLSI Methods

2015 ◽  
Vol 59 (4) ◽  
pp. 1919-1921 ◽  
Author(s):  
Henry S. Heine ◽  
Jeremy Hershfield ◽  
Charles Marchand ◽  
Lynda Miller ◽  
Stephanie Halasohoris ◽  
...  
Keyword(s):  
Yersinia Pestis ◽  
Broth Microdilution ◽  
Content Type ◽  
Microdilution Method ◽  
Reference Information ◽  
Broth Microdilution Method ◽  
Two Temperatures ◽  
Emergence Of Resistance ◽  
Antibiotic Agents

ABSTRACTIn vitrosusceptibilities to 45 antibiotics were determined for 30 genetically and geographically diverse strains ofYersinia pestisby the broth microdilution method at two temperatures, 28°C and 35°C, following Clinical and Laboratory Standards Institute (CLSI) methods. TheY. pestisstrains demonstrated susceptibility to aminoglycosides, quinolones, tetracyclines, β-lactams, cephalosporins, and carbapenems. Only a 1-well shift was observed for the majority of antibiotics between the two temperatures. Establishing and comparing antibiotic susceptibilities of a diverse but specific set ofY. pestisstrains by standardized methods and establishing population ranges and MIC50and MIC90values provide reference information for assessing new antibiotic agents and also provide a baseline for use in monitoring any future emergence of resistance.

scholarly journals In Vitro Antibiotic Susceptibilities of Francisella tularensis Determined by Broth Microdilution following CLSI Methods

2017 ◽  
Vol 61 (9) ◽  
Author(s):  
Henry S. Heine ◽  
Lynda Miller ◽  
Stephanie Halasohoris ◽  
Bret K. Purcell
Keyword(s):  
Francisella Tularensis ◽  
Broth Microdilution ◽  
Content Type ◽  
Microdilution Method ◽  
Reference Information ◽  
Antibiotic Susceptibilities ◽  
Broth Microdilution Method ◽  
Emergence Of Resistance ◽  
Antibiotic Agents

ABSTRACT In vitro susceptibilities for 47 antibiotics were determined in 30 genetic diverse strains of Francisella tularensis by the broth microdilution method following Clinical and Laboratory Standards Institute (CLSI) methods. The F. tularensis strains demonstrated susceptibility to aminoglycosides, fluoroquinolones, and tetracyclines. There was a distinct difference in macrolide susceptibilities between A and B type strains, as has been noted previously. The establishment and comparison of antibiotic susceptibilities of a diverse but specific set of F. tularensis strains by standardized methods and the establishment of population ranges and MIC50/90 values provide reference information for assessing new antibiotic agents and a baseline to monitor any future emergence of resistance, whether natural or intentional.

scholarly journals In Vitro Antibiotic Susceptibilities ofBurkholderia mallei (Causative Agent of Glanders) Determined by Broth Microdilution and E-Test

2001 ◽  
Vol 45 (7) ◽  
pp. 2119-2121 ◽  
Author(s):  
Henry S. Heine ◽  
Marilyn J. England ◽  
David M. Waag ◽  
W. Russell Byrne
Keyword(s):  
Causative Agent ◽  
Burkholderia Mallei ◽  
Broth Microdilution ◽  
Microdilution Method ◽  
Reference Information ◽  
Antibiotic Susceptibilities ◽  
Broth Microdilution Method ◽  
Antibiotic Agents ◽  
Broth Dilution

ABSTRACT In vitro susceptibilities to 28 antibiotics were determined for 11 strains of Burkholderia mallei by the broth microdilution method. The B. mallei strains demonstrated susceptibility to aminoglycosides, macrolides, quinolones, doxycycline, piperacillin, ceftazidime, and imipenem. For comparison and evaluation, 17 antibiotic susceptibilities were also determined by the E-test. E-test values were always lower than the broth dilution values. Establishing and comparing antibiotic susceptibilities of specific B. mallei strains will provide reference information for assessing new antibiotic agents.

scholarly journals In Vitro Activity of Meropenem-Vaborbactam against Clinical Isolates of KPC-Positive Enterobacteriaceae

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Meredith A. Hackel ◽  
Olga Lomovskaya ◽  
Michael N. Dudley ◽  
James A. Karlowsky ◽  
Daniel F. Sahm
Keyword(s):  
Clinical Isolates ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
Content Type ◽  
Class A ◽  
Microdilution Method ◽  
Fixed Concentration ◽  
Broth Microdilution Method ◽  
The U.S

ABSTRACT Vaborbactam (formerly RPX7009) is a novel inhibitor of serine β-lactamases, including Ambler class A carbapenemases, such as KPCs. The current study evaluated the in vitro activity of the combination agent meropenem-vaborbactam against a global collection of 991 isolates of KPC-positive Enterobacteriaceae collected in 2014 and 2015 using the Clinical and Laboratory Standards Institute (CLSI) standard broth microdilution method. The MIC90 of meropenem (when tested with a fixed concentration of 8 μg/ml of vaborbactam) for isolates of KPC-positive Enterobacteriaceae was 1 μg/ml, and MIC values ranged from ≤0.03 to >32 μg/ml; 99.0% (981/991) of isolates had meropenem-vaborbactam MICs of ≤4 μg/ml, the U.S. FDA-approved MIC breakpoint for susceptibility to meropenem-vaborbactam (Vabomere). Vaborbactam lowered the meropenem MIC50 from 32 to 0.06 μg/ml and the MIC90 from >32 to 1 μg/ml. There were no differences in the activity of meropenem-vaborbactam when the isolates were stratified by KPC variant type. We conclude that meropenem-vaborbactam demonstrates potent in vitro activity against a worldwide collection of clinical isolates of KPC-positive Enterobacteriaceae collected in 2014 and 2015.

scholarly journals Revised Reference Broth Microdilution Method for Testing Telavancin: Effect on MIC Results and Correlation with Other Testing Methodologies

2014 ◽  
Vol 58 (9) ◽  
pp. 5547-5551 ◽  
Author(s):  
David J. Farrell ◽  
Rodrigo E. Mendes ◽  
Paul R. Rhomberg ◽  
Ronald N. Jones
Keyword(s):  
Susceptibility Testing ◽  
Previous Method ◽  
Broth Microdilution ◽  
Content Type ◽  
Testing Method ◽  
Microdilution Method ◽  
Drug Potency ◽  
Broth Microdilution Method ◽  
Plastic Surfaces

ABSTRACTThe reference broth microdilution (BMD) antimicrobial susceptibility testing method for telavancin was revised to include dimethyl sulfoxide (DMSO) as a solvent and diluent for frozen-form panel preparation, following the CLSI recommendations for water-insoluble agents. Polysorbate 80 (P-80) was also added to the test medium to minimize proven drug losses associated with binding to plastic surfaces. Four hundred sixty-two Gram-positive isolates, including a challenge set of organisms with reduced susceptibilities to comparator agents, were selected and tested using the revised method for telavancin, and the MIC results were compared with those tested by the previously established method and several Sensititre dry-form BMD panel formulations. The revised method provided MIC results 2- to 8-fold lower than the previous method when tested against staphylococci and enterococci, resulting in MIC50values of 0.03 to 0.06 μg/ml for staphylococci and 0.03 and 0.12 μg/ml forEnterococcus faeciumandEnterococcus faecalis, respectively. Less-significant MIC decreases (1 to 2 log2dilution steps) were observed when testing streptococci in broth supplemented with blood, which showed similar MIC50values for both methods. However,Streptococcus pneumoniaehad MIC50results of 0.008 and 0.03 μg/ml when tested by the revised and previous methods, respectively. Highest essential agreement rates (≥94.0%) were noted for one candidate dry-form panel formulation compared to the revised test. The revised BMD method provides lower MIC results for telavancin, especially when tested against staphylococci and enterococci. This is secondary to the use of DMSO for panel production and the presence of P-80, which ensure the proper telavancin testing concentration and result in a more accurate MIC determination. Moreover, earlier studies where the previous method was applied underestimated thein vitrodrug potency.

scholarly journals In VitroAmphotericin B Susceptibility of Malassezia pachydermatis Determined by the CLSI Broth Microdilution Method and Etest Using Lipid-Enriched Media

2014 ◽  
Vol 58 (7) ◽  
pp. 4203-4206 ◽  
Author(s):  
Sergio Álvarez-Pérez ◽  
José L. Blanco ◽  
Teresa Peláez ◽  
Maite Cutuli ◽  
Marta E. García
Keyword(s):  
High Activity ◽  
Amphotericin B ◽  
Yeast Species ◽  
Broth Microdilution ◽  
Malassezia Pachydermatis ◽  
Content Type ◽  
Microdilution Method ◽  
Broth Microdilution Method

ABSTRACTWe determined thein vitroamphotericin B susceptibility of 60Malassezia pachydermatisisolates by the CLSI broth microdilution method and the Etest using lipid-enriched media. All isolates were susceptible at MICs of ≤1 μg/ml, confirming the high activity of amphotericin B against this yeast species. Overall, the essential agreement between the tested methods was high (80% and 96.7% after 48 h and 72 h, respectively), and all discrepancies were regarded as nonsubstantial.

scholarly journals In VitroSusceptibility of Pythium insidiosum Isolates to Aminoglycoside Antibiotics and Tigecycline

2012 ◽  
Vol 56 (7) ◽  
pp. 4021-4023 ◽  
Author(s):  
Deise Luiza Mahl ◽  
Francielli Pantella Kunz de Jesus ◽  
Érico Silva Loreto ◽  
Régis Adriel Zanette ◽  
Laerte Ferreiro ◽  
...  
Keyword(s):  
Aminoglycoside Antibiotics ◽  
Good Option ◽  
Broth Microdilution ◽  
Pythium Insidiosum ◽  
Content Type ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Susceptibility Tests

ABSTRACTThis study evaluated thein vitroactivity of aminoglycoside antibiotics and tigecycline againstPythium insidiosum. The susceptibility tests were carried out using the broth microdilution method in accordance with the CLSI document M38-A2. MIC values for gentamicin, neomycin, paromomycin, and streptomycin ranged from 32 to 64 mg/liter, and the minimal fungicidal concentration (MFC) ranged from 32 to 128 mg/liter, which are incompatible with safe concentrations of these drugs in plasmain vivo. Tigecycline showed the lowest MIC (0.25 to 2 mg/liter) and MFC (1 to 8 mg/liter) range values. Thein vitrosusceptibility observed to tigecycline makes this drug a good option in future testsin vitroandin vivofor the management of pythiosis.

scholarly journals Activity of Ceftazidime-Avibactam against Fluoroquinolone-Resistant Enterobacteriaceae and Pseudomonas aeruginosa

2015 ◽  
Vol 59 (6) ◽  
pp. 3059-3065 ◽  
Author(s):  
C. Pitart ◽  
F. Marco ◽  
T. A. Keating ◽  
W. W. Nichols ◽  
J. Vila
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Resistant Mutant ◽  
Fluoroquinolone Resistance ◽  
Cross Resistance ◽  
Content Type ◽  
E Coli ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
The Impact

ABSTRACTCeftazidime-avibactam and comparator antibiotics were tested by the broth microdilution method against 200Enterobacteriaceaeand 25Pseudomonas aeruginosastrains resistant to fluoroquinolones (including strains with the extended-spectrum β-lactamase [ESBL] phenotype and ceftazidime-resistant strains) collected from our institution. The MICs and mechanisms of resistance to fluoroquinolone were also studied. Ninety-nine percent of fluoroquinolone-resistantEnterobacteriaceaestrains were inhibited at a ceftazidime-avibactam MIC of ≤4 mg/liter (using the susceptible CLSI breakpoint for ceftazidime alone as a reference). Ceftazidime-avibactam was very active against ESBLEscherichia coli(MIC90of 0.25 mg/liter), ESBLKlebsiella pneumoniae(MIC90of 0.5 mg/liter), ceftazidime-resistant AmpC-producing species (MIC90of 1 mg/liter), non-ESBLE. coli(MIC90of ≤0.125 mg/liter), non-ESBLK. pneumoniae(MIC90of 0.25 mg/liter), and ceftazidime-nonresistant AmpC-producing species (MIC90of ≤0.5 mg/liter). Ninety-six percent of fluoroquinolone-resistantP. aeruginosastrains were inhibited at a ceftazidime-avibactam MIC of ≤8 mg/liter (using the susceptible CLSI breakpoint for ceftazidime alone as a reference), with a MIC90of 8 mg/liter. Additionally, fluoroquinolone-resistant mutants from each species tested were obtainedin vitrofrom two strains, one susceptible to ceftazidime and the other a β-lactamase producer with a high MIC against ceftazidime but susceptible to ceftazidime-avibactam. Thereby, the impact of fluoroquinolone resistance on the activity of ceftazidime-avibactam could be assessed. The MIC90values of ceftazidime-avibactam for the fluoroquinolone-resistant mutant strains ofEnterobacteriaceaeandP. aeruginosawere ≤4 mg/liter and ≤8 mg/liter, respectively. We conclude that the presence of fluoroquinolone resistance does not affectEnterobacteriaceaeandP. aeruginosasusceptibility to ceftazidime-avibactam; that is, there is no cross-resistance.

scholarly journals In Vitro Activities of the Novel Oxazolidinones DA-7867 and DA-7157 against Rapidly and Slowly Growing Mycobacteria

2006 ◽  
Vol 50 (12) ◽  
pp. 4027-4029 ◽  
Author(s):  
Lucio Vera-Cabrera ◽  
Barbara A. Brown-Elliott ◽  
Richard J. Wallace ◽  
Jorge Ocampo-Candiani ◽  
Oliverio Welsh ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Isolates ◽  
Nontuberculous Mycobacterium ◽  
The Novel ◽  
Broth Microdilution ◽  
Reference Species ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Aerobic Actinomycetes

ABSTRACT DA-7867 and DA-7157 are oxazolidinones active against pathogenic aerobic actinomycetes including Nocardia spp. and Mycobacterium tuberculosis. However, the activity of these drugs against nontuberculous mycobacterium (NTM) species is not known. In this work, we compared the susceptibilities of 122 clinical isolates and 29 reference species of both rapidly growing and slowly growing mycobacteria to linezolid, DA-7867, and DA-7157 by the broth microdilution method. The MICs for 50 and 90% of the strains tested (MIC50s and MIC90s, respectively) of DA-7867 and DA-7157 were lower than those of linezolid. In all of the cases, a MIC90 of <8 μg/ml was observed for all of the species tested in both groups of NTM. For M. kansasii and M. marinum isolates, the MIC90s of both DA-7867 and DA-7157 were less than 0.5 μg/ml. These results demonstrate the potential of these compounds to treat NTM infections.

scholarly journals In Vitro Activities of the New Antifungal Triazole SCH 56592 against Common and Emerging Yeast Pathogens

2000 ◽  
Vol 44 (1) ◽  
pp. 226-229 ◽  
Author(s):  
Francesco Barchiesi ◽  
Daniela Arzeni ◽  
Annette W. Fothergill ◽  
Luigi Falconi Di Francesco ◽  
Francesca Caselli ◽  
...  
Keyword(s):  
Clinical Laboratory ◽  
Clinical Development ◽  
National Committee ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Vitro Data ◽  
In Vitro Data

ABSTRACT A broth microdilution method performed in accordance with the National Committee for Clinical Laboratory Standards guidelines was used to compare the in vitro activity of the new antifungal triazole SCH 56592 (SCH) to that of fluconazole (FLC), itraconazole (ITC), and ketoconazole (KETO) against 257 clinical yeast isolates. They included 220 isolates belonging to 12 different species of Candida, 15 isolates each of Cryptococcus neoformans andSaccharomyces cerevisiae, and seven isolates ofRhodotorula rubra. The MICs of SCH at which 50% (MIC50) and 90% (MIC90) of the isolates were inhibited were 0.06 and 2.0 μg/ml, respectively. In general, SCH was considerably more active than FLC (MIC50 and MIC90 of 1.0 and 64 μg/ml, respectively) and slightly more active than either ITC (MIC50 and MIC90 of 0.25 and 2.0 μg/ml, respectively) and KETO (MIC50 and MIC90 of 0.125 and 4.0 μg/ml, respectively). Our in vitro data suggest that SCH has significant potential for clinical development.

scholarly journals Evaluation of a Modified EUCAST Fragmented-Mycelium Inoculum Method forIn VitroSusceptibility Testing of Dermatophytes and the Activity of Novel Antifungal Agents

2015 ◽  
Vol 59 (6) ◽  
pp. 3675-3682 ◽  
Author(s):  
B. Risslegger ◽  
C. Lass-Flörl ◽  
G. Blum ◽  
M. Lackner
Keyword(s):  
Antifungal Agents ◽  
Susceptibility Testing ◽  
Preparation Method ◽  
Antifungal Susceptibility ◽  
Broth Microdilution ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Inoculum Preparation ◽  
Minimal Effective Concentration

ABSTRACTFor antifungal susceptibility testing of nonsporulating or poorly sporulating dermatophytes, a fragmented-mycelium inoculum preparation method was established and compared to broth microdilution testing according to CLSI and EUCAST guidelines. Moreover, thein vitroactivity of new antifungal agents against dermatophytes was evaluated. Agreement between the mycelial inoculum method and the CLSI broth microdilution method was high (93% to 100%). Echinocandins (minimal effective concentration [MEC], ≤0.5 mg/liter) and posaconazole (MIC, ≤3.00 mg/liter) showed good activity against all tested dermatophytes.

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